Spatial Organization of Biological Fuctions | BPS Thematic Meeting

Spatial Organization of Biological Functions Meeting

Thursday Speaker Abstracts

DECODING SPATIAL SELECTIVITY IN CHAPERONE-MEDIATED AUTOPHAGY Nidhi Malhotra 1 ; 1 Shiv Nadar Institution of Eminence, Delhi NCR, Department of Chemistry, Greater Noida, India Chaperone-mediated autophagy (CMA) is a selective lysosomal degradation pathway critical for maintaining cellular proteostasis, particularly under stress and aging-related conditions. The process involves the recognition of cytosolic proteins containing KFERQ-like motifs by heat shock cognate protein 70 (HSC70), followed by their targeting to the lysosomal membrane. At the membrane surface, substrates are bound by lysosome-associated membrane protein type 2A (LAMP2A), which undergoes regulated multimerization to facilitate substrate unfolding, translocation into the lysosomal lumen, and subsequent degradation. While the functional significance of CMA is well established, the molecular determinants underlying its substrate selectivity and spatial coordination remain poorly defined. In this study, we employed multiple microsecond atomistic molecular dynamics (MD) simulations to elucidate two key spatial features governing CMA efficiency. First, we examined structural changes induced by modulating charges in the juxtamembrane region of LAMP2A, as well as by introducing a non functional four-residue mutation in the same region. Our analysis suggests that these alterations lead to local conformational changes that misalign substrate-binding surfaces and destabilize multimer assembly, potentially impairing substrate internalization. Second, using a combination of AlphaFold 3 predictions and ~44 microseconds of all-atom MD simulations, we characterized the HSC70–substrate interface across 15 human CMA substrates and identified secondary substrate-binding regions on HSC70 that may contribute to the formation of an extended interaction interface. Together, these findings provide mechanistic insights into how spatial alterations influenced by electrostatic environment, conformational dynamics and binding landscape, shape the molecular architecture of CMA, with potential implications for its selectivity, efficiency, and dysfunction.

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